In boost pressure control, it may occur that a fault in the operation of the internal combustion engine (e.g., a combustion miss) or faulty sensors (e.g., air pressure sensor, air mass flow sensor) causes the speed of the turbocharger to be adjusted upward into a critical range and the turbocharger is permanently damaged as a result. German Patent No. 195 13 156 describes that this problem occurs, in particular, in internal combustion engines having two rows of cylinders with one turbocharger each. If one of the two turbochargers is in fact defective or a catalytic converter is clogged in one of the two exhaust lines, the control circuit will balance the system deviation of the actual boost pressure value from the setpoint boost pressure value caused by the fault occurring on one side by increasing the speed of the turbocharger on the side without a fault. In doing so, the speed of the turbocharger can reach a critical value, resulting in permanent damage to the turbocharger. In order to preclude permanent damage to a turbocharger in the event of a fault, as described in German Patent No. 195 13 156, the closed-loop control is switched off and a switchover is made to an open-loop control if a fault recognition device detects a fault in one side of the two exhaust gas lines. The open-loop control is designed in such a way that the speed of the turbocharger is not increased into its critical speed range. In contrast to closed-loop control, the actual value of charge air or air mass no longer has an influence on the control signal for the turbocharger in the event of a fault in open-loop control. The open-loop control limits the speed of the turbocharger to a constant value. In many types of faults, this value represents an overreaction in limiting the speed of the turbocharger to a constant value.
A control device for an internal combustion engine is described in U.S. Pat. No. 5,497,751, which provides two controllers for the control of the ignition and/or fuel injection for the individual cylinders. The identical input variables, which are provided by separate sensors, are supplied to both controllers so that both controllers make the same control information available to the ignition and/or injection device of the internal combustion engine. The control device therefore has a second controller in order to increase the reliability in an engine used in an airplane.
The objective of the present invention is to provide an arrangement that reacts with flexible control of the turbocharger in the event of a fault.